1. Field of the Invention
The present invention relates to a method of and apparatus for concealing an error of a frame in the time domain, and more particularly, to a frame error concealment method and apparatus, in which an error of a frame, i.e., a frame error, is concealed by reconstructing a signal of the frame using a signal of a previous frame preceding the error frame and/or a signal of a next frame following the error frame.
2. Description of the Related Art
When some packets are lost or distorted during transmission of an encoded audio signal over a wired/wireless network, an error may be generated in a frame of a decoded audio signal due to a transmission error. Error concealment may be classified into a frequency-domain error concealment scheme and a time-domain error concealment scheme. The frequency-domain error concealment scheme may be divided into a repetition method that reconstructs a signal of an error frame by reusing spectrum coefficients of a previous frame in the error frame and an interpolation method that reconstructs spectrum coefficients of an error frame by interpolating spectrum coefficients of a previous frame and a next frame. However, due to characteristics of Modulated Discrete Cosine Transformation (MDCT) that transforms a time-domain signal into a frequency-domain signal, when the window types of a previous frame and the current frame are different from each other or a burst error occurs, an error of a frame, i.e., a frame error, cannot be concealed using the repetition method or the interpolation method in the frequency domain. In this case, therefore, time-domain error concealment is required.
The time-domain error concealment scheme can also be divided into a repetition method that repetitively reproduces a time-domain sample of a previous frame in an error frame, an interpolation method that reconstructs a time-domain sample of an error frame by interpolating time-domain samples of a previous frame and a next frame, and other methods that reconstruct a signal of an error frame by analyzing a signal of a previous frame. However, in the case of the repetition method in the time domain, when an error occurs over a long interval, the same spectrum signal of a previous frame is repeated over the long interval, causing modulation noise. Moreover, since the interpolation method in the time domain conceals an error with reference to a next frame, it is not easy to use the interpolation method when an error occurs over a long interval. The other methods for time-domain error concealment increase complexity due to the analysis of a signal of a previous frame.